Analyzing a lake ecosystem is an interesting and everlasting area of Environmental Studies. Since these water bodies are subjected to pollution and degradation, analyzing them is an essential requirement. These analytical works come under a special branch of Science called Limnology.

1. BY
PROF. A. BALASUBRAMANIAN
Centre for Advanced Studies in Earth Science
University of Mysore, India

2. •large in-land bodies of fresh or salt water
•good aquatic ecosystems providing a lot of
benefits to human beings and to animal life
•slow-moving or standing water bodies
with good water resource and biodiversity
• used as water sources for drinking,
domestic utilization , irrigation and
recreation

3. •A lake moderates the surrounding region’s
temperature and climate and thereby attracting
people to settle around.
•Many lakes are used for developing fisheries and
aquaculture.
•City dwellers establish pathways around a lake.
These tracks help them to walk around every day.
•Boating is a good recreational activity for
children and adults in a lake.

4. •People cut the aquatic plants and supply
them as fodder to cattle and also use them
for general purposes.
•The flowers of lake vegetation are unique
collections for selling and decorations.
•Many towns and municipalities survive
only with lake water as their primary
source of drinking water to the entire
population.

5. •Analyzing a lake ecosystem is an
interesting and everlasting area of
Environmental Studies
•Since these water bodies are subjected to
pollution and degradation, analyzing them
is an essential requirement
•These analytical works come under a
special branch of Science called Limnology

6. Limnology is the scientific study of inland water
bodies.
It may be a pond, lake, river, estuary with fresh
or saline waters.
It is a unique branch comprising many
interdisciplinary subjects like
Geology, Hydrology, Meteorology , Botany,
Zoology, Physics, Chemistry, Ecology,
Environmental Science, Fishery Biology, Civil
Engineering, Environmental Engineering and
Pollution Control.

7. Since lakes are aquatic ecosystems with various
biotic and a biotic factors, Limnological Research
involves an interdisciplinary analysis.
The methodology of research in limnology may be
the same but the application area may be different
like a lake or a river or an estuary.
Each one of these have their own uniqueness in
water quantity, quality, fauna, flora and
dynamism.
Sometimes, inland seas are considered for
limnological studies.

8. •Lakes are extremely varied in terms of
origin, occurrence, size, shape, depth, water
chemistry, and other features.
•They are dynamic ecosystems.
•Most of them are under the direct or indirect
influences of human activities and
development.
•A lot of factors lead to the deterioration of
lakes and their survival.

9. •Protection of a lake from pollution or
degradation is a major aspect of development.
•Intelligent utilization of a lake’s all natural
resources requires a detailed analysis.
•In this module, let us see the factors which are
very essential while analysing a lake as an
ecosystem.

10. 1. GEOGRAPHIC SETTING
2. MORPHOMETRY OF A LAKE
3. WATERSHED CHARACTERISTICS
4. CLIMATOLOGY
5. HYDROLOGY
6. HYDROCHEMISTRY
7. ENVIRONMENTAL BIOLOGY
8. SEDIMENTOLOGY
9. MICROBIOLOGY
10. POLLUTION AND POLLUTANTS
11. TROPHIC STATE & EUTROPHICATION
12. RESTORATION.

11. The location of a lake and its geographic setting
are to be understood first.
Its Boundary , latitude, longitude and altitude.
Origin of the lake- Natural (Glacial/Tectonic/
Volcanic/ erosional ); Artificial ( Reservoirs,
waterworks)
Ownership - National/ State ; Riparian
jurisdictions
Demographic conditions

12. •Lakes are characterized by their basin
morphometry which is the actual depression
holding the water and its physiography.
•This analysis involves the measurement of
surface area , Depth and thickness of water
column and volume of lake water available in
storage, the shorelines, their shape and areal
extent .
•Bathymetric charts are prepared for this purpose.

13. •Every lake belongs to a watershed with its own isolated or
regional catchment area.
•This includes the topography, drainage network and
other surface water resources which have direct or
indirect influence.
•Landuse- agriculture, urbanization, industrialization,
lawns, parks, infrastructural development.
•Landcover – vegetation and forest cover, soils, grassland,
marshy land, wasteland, rangeland,
•Major Geological features- Rock types – Distribution.
•Structures like Faults , Lineaments and joints.
•Dykes and surface exposures.

14. •Lakes are mainly influenced by the regional or
local climate and weather systems.
•Since climate has a direct role in most of the
processes that happen in a lake, meteorological
parameters are to be analysed thoroughly.
•Daily variation in Temperature, Sun shine hours ,
rainfall, Evapotranspiration, humidity in air, wind
velocity and direction, atmospheric pressure ,
evaporation and interception.

15. •The quantity of water existing within a lake and the inflow-
outflow volumes are very essential in understanding the
dynamics of a lake.
•These depends on the basin size, rainfall pattern, runoff
components, soils profile, infiltration of soils,
evapotranspiration, diversions, and recharge into
groundwater systems.
•Water balance of a lake with reference to time is a basic
requirement.
•The relationship between rainfall, inflow-outflow,
consumption by various organisms and processes are also
related to lake water levels.
•The chemistry of lake water is also controlled by the
quantity of inflow and pollutant load carried by it.

16. •The quality of water in a lake is determined by its
• Physical Properties
• Chemical composition
• Biological Properties and
• Pollutant characteristics.
•Without analysing these properties,
research on lake as ecosystems may have
little significance.

17. •Surface water temperature, color, odour
•Thermal stratification with depth.
•Light penetration
•Turbidity
•Transparency level using Secchi disks at all
locations.

18. •Electrical conductivity, Total Dissolved Solids
•pH
•Oxidation-Reduction Potential
•Major Cations- Calcium, Magnesium, Sodium,
Potassium
•Major Anions- Bicarbonate, Carbonate , Chloride,
Sulphate, Fluoride.
•Trace Elements- Iron, Aluminum, Copper, Nickel,
Cadmium, Chromium, Lead, Zinc, Mercury, Arsenic,
and Cobalt.
•Nutrients- Nitrates & Phosphate.
•Ammonical Nitrogen.

19. •Dissolved Oxygen
•Biochemical Oxygen Demand
•Chemical Oxygen Demand
•Volatile Organic Carbon
•Total Coliform
•Feacal Coliform

20. •Phytoplankton, Zooplankton
•Benthic fauna and flora, Nektons
•Macrophytes, Biomass, Productivity
•Emergent vegetation, invasive plants
•Species density and composition
•Biodiversity , Fish species
•Birds , fouls and other animals.
•Uptake of nutrients by plants and animals
•Growth rates, excretion rates, mortality rates and
settling rates.

21. •Lake sediments are called as lacustrine
deposits.
•Inflowing water carries a lot of
sediments into a lake.
•Pollutants and nutrients may travel
through inflow.
•Suspended and bed load sediments
may enter into a lake during every
season of rainfall.

22. •Urban sewage water may also add to
these volumes.
•Chemistry of sediments are to be
analysed with reference to their major
ions, trace metals and nutrients
•Data of Daily , monthly and annual
sediment loads are essential while
analysing the lake dynamics.
•Rate of siltation and their impact on
the volume of water storage.

23. •The material at the bottom of a lake, or
lake bed, may be composed of a wide
variety of inorganics, such as silt or sand,
and organic material, such as decaying
plant or animal matter.
•The composition of the lake bed has a
significant impact on the flora and fauna
found within the lake's environs by
contributing to the amounts and the types
of nutrients available.

24. Diatoms, algae, fungi
Bacteria,- pathogenic and non-pathogenic
Solmonella
Microbial mobility
Decaying rates

25. Domestic pollution- pollutants
Municipal Sewage water inflow
Urban storm drainage water inflow
Industrial sewage or effluent, if any
Agricultural runoff
Agrochemical inputs
Cleaning of automobiles
Oil spills from boating operations
Other human disturbances.

26. •The trophic state of a lake is determined based on various
physico-chemical parameters which we have seen just now.
•The quantities of nitrogen, phosphorus, and other biologically
useful nutrients are the primary determinants of a lake's
trophic state index (TSI).
•Nutrients tend to be the limiting resources in standing water
bodies, so increased concentrations will result in the
increased plant growth, followed by corollary increases in
subsequent trophic levels.
•Consequently, a lake's trophic index may sometimes be used
to make a rough estimate of its biological condition.

27. Lakes can be also categorized on the basis of
their richness in nutrients, which
typically affect their plant growth.
Nutrient-poor lakes are said to be
oligotrophic lakes and are generally clear,
having a low concentration of plant life.
Mesotrophic lakes have good clarity and
contain an average level of nutrients.
Eutrophic lakes are fully enriched with
nutrients, resulting in good plant growth and
possible algal blooms. This itself may affect
the life of the lake.

28. •Hypertrophic lakes are bodies of water that
have been excessively enriched with
nutrients.
•These lakes typically have poor clarity and
are subject to devastating algal blooms.
•Lakes typically reach this condition due to
human activities, such as heavy use of
fertilizers in the lake catchment area.
•Such lakes are of little use to humans and
have a poor ecosystem due to decreased
dissolved oxygen.

29. It is necessary to protect the life of every lake.
Lakes need continuous monitoring and
protection.
Once the ecosystem is disturbed then
restoration becomes a tedious and expensive
affair.
Silt control, weed control, pollutant load
control, aeration and inflow management are
essential steps.

30. •It is our duty to conserve and preserve the natural
resources.
•Detailed analysis of the ecology of such natural
resources will alone help us to understand and go for
proper management methods.
•Analysing lakes will be an interesting research area
for all geographers, geologists, environmentalists,
biologist, chemists, experts in physics, biochemistry,
naturalists, engineers , economists, taxonomists, and
town planners.
•The preliminary methods have alone been seen now.
•Further information is also available for researchers
in various forms.

31. Thank you